#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<cstdio>
#include<algorithm>

using namespace std;

int main()
{
    int x, y, sum;
    cin >> x >> y;
    if (x > y)
        swap(x, y);
    for (int i = x + 1; i < y; i++)
    {
        if (i % 2)
            sum += i;
    }
    cout << sum << endl;
    return 0;
}